Triceps brachii muscle

The triceps brachii muscle (Latin for "three-headed arm muscle") is the large muscle on the back of the upper limb of many vertebrates. It is the muscle principally responsible for extension of the elbow joint (straightening of the arm).

Terminology

It is called a three-headed muscle because there are three bundles of muscles, each of different origins, joining together at the elbow. Though a similarly named muscle, the triceps surae, is found on the lower leg, the triceps brachii is commonly called the "triceps".

Historically, the plural form of the adjective triceps was tricipites, a form not in general use today; instead triceps is used in both singular and plural (i.e., when referring to both arms). The triceps also make up approximately 2/3 of the muscle mass in the arm.

Human anatomy

Origins

The long head arises from the infraglenoid tubercle of the scapula. It extends distally anterior to the teres minor and posterior to the teres major.

The medial head arises distally from the groove of the radial nerve; from the dorsal (back) surface of the humerus; from the medial intermuscular septum; and its distal part also arises from the lateral intermuscular septum. The medial head is mostly covered by the lateral and long heads, and is only visible distally on the humerus.

The lateral head arises from the dorsal surface of the humerus, lateral and...
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